Multifilament yarn core/sheath constructions are known. An example of such a construction is US 200810009903A1. Multifilament yarn core/sheath constructions are typically utilized to obtain a construction with lower bending fatigue. Furthermore, multifilament core/sheath constructions typically behave plastic upon bending without much—if any—elastic deformation. The plasticity under bending is typically associated with local bending stresses. In other words, the resistance against bending deformation is very small.
When the yarn is a thermoplastic yarn, the stiffness of multifilament yarn constructions may be increased by heat treating the construction to a level where the yarns at least partially fuse together to form a monofilament-like sheath for example as disclosed in EP 1 771 213. However, monofilaments and monofilament-like constructions typically behaves elastic upon bending at smaller bending angles without leaving much—if any—plastic deformation after removal of the bending force. For large bending at sharp angles monofilament and monofilament-like constructions may deform plastically, however, such plastic deformation will introduce considerably damage to the monofilament construction.
Other multifilament core/sheet construction are disclosed in U.S. Pat. No. 3,968,725 (Holzhauer), EP 1 293 218 (Grafton et al.) and WO 2009/142766.